Grooves have been cut in airport runways and road surfaces to facilitate water run-off and prevent hydroplaning. The typical airport runway groove is 1/4 inch of an inch wide by 1/4 of an inch deep. The usual spacing between grooves varies from 3/4 of an inch or less to 4 inches or more. A major airport runway may thus have millions of linear feet of grooves cut into it. These grooves can be cut by a series of spaced rotating tools, each carrying cutting elements spaced about their periphery. The cutting elements have a rectangular cross-sectional shape corresponding to the desired dimensions of the final grooves. Because of the fact that each longitudinal segment of the cutting element cuts or abrades the same amount of material as the next adjacent segment, the cutting elements wear uniformly, thereby producing the desired shaped groove during their entire cutting life.
Square grooves, particularly in airport runways, have certain inherent disadvantages. They are difficult to keep clean; they are subject to having their edges chipped by snow plows; and, most important, particularly in asphalt runways, the grooves tend to close due to the impact of airplanes taking off, landing and braking. This necessitates a regrooving of the runway requiring extended periods of closing the runway.
In the early days of grooving runways, V-shaped grooves and trapezoidal grooves, wider at the top than at the bottom were found effective. They are easier to clean, resist damage by snowplows, and resist peening over or closing by landing aircraft. However, such grooves were soon abandoned because of the lack of the ability to produce such grooves of uniform configuration from one end of the runway to the other. To produce a V-shaped groove with the cutting tool rotating about a horizontal axis, the cutting elements must also be V-shaped. In cutting with such a tool, the tip of the V or the apex cuts a quantity of material equal to the depth of the groove, while the edge of the tool remote from the apex cuts infinitely less material. This results in uneven wear causing the cutting element to become rounded in cross sectional shape, requiring frequent stopping of the cutting operation and redressing of each cutting tool. Because of these problems, square grooves in runways became the standard in the industry despite their drawbacks.
Cutting tools of this type will have many uses other than cutting grooves as described above. One major use can be in routing cracks in any type of paving for the purpose of preparing the crack to receive a sealant for protection against further damage. Other uses can be either straight or rounded champhering of edges of material and forming ornamental concave, convex or other surfaces in a substrate.
With the foregoing in mind, it is the object of the present invention to provide a novel cutting element for material which will cut other than a square groove or form a contoured shape on the surface of the material and which will maintain its original cross sectional shape through extended usage and wear.
It is a further object of the present invention to provide a novel cutting or abrading element in which that portion of the cutting element which must cut or abrade the deepest has the longest dimension in the direction of movement of the cutting element and that portion which cuts the least has the shortest such dimension to provide uniform wear to the surface of the cutting element.
Other objects of the invention will be apparent from the following description.